1. Field of the Invention
The present invention relates to a positive resist composition suitable for use in the ultramicrolithography process such as production of VLSI or a high-capacity microchip or in other photofabrication processes, and a pattern forming method using the composition. More specifically, the present invention relates to a positive resist composition capable of forming a high-resolution pattern by using KrF excimer laser light, electron beam, EUV light or the like, and a pattern forming method using the composition. That is, the present invention relates to a resist composition suitably usable for fine processing of a semiconductor device, where KrF excimer laser light, electron beam or EUV light is used, and a pattern forming method using the composition.
2. Description of the Related Art
In the process of producing a semiconductor device such as IC and LSI, fine processing by lithography using a photoresist composition has been conventionally performed. Recently, the integration degree of an integrated circuit is becoming higher and formation of an ultrafine pattern in the sub-micron or quarter-micron region is required. To cope with this requirement, the exposure wavelength also tends to become shorter, for example, from g line to i line or further to KrF excimer laser light. At present, other than the excimer laser light, development of lithography using electron beam, X ray or EUV light is proceeding.
In the lithography employed for the ion injection step using KrF excimer laser light, it is an important issue to satisfy all performances in terms of high resolution, number of development defects and iso-dense bias in the ultrafine region, and this problem needs to be solved.
As regards the resist suitable for the lithography process used in such an ion injection step, a chemical amplification-type resist formulated to adjust the light transparency of the resist film is supposed to be effective from the standpoint of controlling the resist pattern profile on a high-reflection substrate and as disclosed in JP-A-7-84364 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-7-316268, JP-A-7-319155, JP-A-10-186647, JP-A-2006-328241 and JP-A-2000-284482, in the case of a positive resist, a chemical amplification-type resist composition mainly comprising a phenolic polymer insoluble or sparingly soluble in an alkali developer but becoming soluble in an alkali developer under the action of an acid (hereinafter simply referred to as a “phenolic acid-decomposable resin”), an acid generator, and a coloring matter for adjusting the light transparency has been proposed.
There is also known a case where the coloring matter for adjusting the light transparency is connected to a phenolic acid-decomposable resin. As regards the coloring matter for adjusting the light transparency, an anthracene structure, a benzenecarboxylic acid structure, a naphthalenecarboxylic acid structure, a thiophene structure and the like are known.
However, by any combination of these techniques, it is impossible at present to satisfy the performances in terms of high resolution, number of development defects and iso-dense bias in the ultrafine region.